X-ray systems are nowadays to be assigned mostly in a dedicated fashion to a clinical application field. A distinction is thus made between angiography systems, fluoroscopy systems and radiography systems. In this classification, the two first-mentioned system groups can cover both dynamic applications as well as also single shots. Angiography, sonography, computer tomography, magnetic resonance tomography and optical coherence tomography are primarily available for the examination of blood vessels. The gold standard for the examination of vessels is angiography however. With interventions, i.e. if the examination achieves in making a narrowing of a vessel visible, in order to extend this and/or keep it open using a stent, there are currently no alternatives to angiography. Rotation angiography systems with a moveable C-arm are preferably used in order to record three-dimensional images of vessels.
Envelopes for the outer dimensions of a patient were previously assumed in order to avoid a collision between the moveable C-arm and the patient, said envelopes being disposed around the patient like a virtual balloon. The envelopes, which are stored in the collision computer of the angiography system, are assumed to be static and consist of several cylinders. In this way, provision can be made for instance for a cylinder for the head, a cylinder for the trunk, two for the arms and one for the legs. Irrespective of the actual size of the patient to be examined, only one static envelope exists, which has nothing to do with the specific silhouette of the patient. If the C-arm of the angiography system approaches the static envelope, the C-arm slows down. In order to protect patients of any body shape and size from colliding with the C-arm during the examination, the static envelope has to be dimensioned very large.
With the recordings according to the above prior art, a slow, manually controlled movement first takes place without x-rays, during which a collision computer is active, with it being monitored whether a collision of the C-arm with the table or with the static patient envelope, formed from the cylinders, occurs. A rapid imaging movement then takes place, during which the x-rays are applied. In this way, the collision computer is no longer active and the doctor is also no longer able to intervene. During the examination, the patient is assumed to be immobile.
US application US 2005/0281374 A1 discloses a prior art which claims a patient positioning system for a therapeutic radiation system with moveable components. The patient positioning system plans movements in advance and analyses these in order to increase the efficiency of the movement in the case of less latency time and to proactively avoid collisions. The patient positioning system contains a number of cameras, which can determine both the location of fixed and moveable system components as well as an infiltration of foreign objects or personal in the movement path. If a collision is impending, the system inhibits the movement of the patient positioning system. The fact that even the patient is also assumed to be immobile here is particularly characteristic of the aforementioned US application.
Electromechanical driving switches are used as a final means of stopping the system, before a patient is seriously injured by colliding with the C-arm. Such a switch can be integrated into the cladding of the C-arm for instance. The switches can be formed as limit switches, cut-off rubbers, tread mats etc.
The problem thus consists in the angiography system described in the prior art not being able to detect a movement of the patient during the examination using x-rays and thus not being able to get sufficiently close to the patient as a result of the large dimensioning of static envelopes of the C-arm at many points.